1. Technical Field
The present invention relates generally to a process of producing a single crystal, and more particularly to a crystal growth apparatus and a thermal insulation cover of the crystal growth apparatus.
2. Description of Related Art
To make a single crystal, a solid material is heated and melted in a crystal growth apparatus, and then a seed crystal is immersed into the melted material to start crystal growth. A conventional crystal growth apparatus includes a crucible and a plurality of heaters, wherein the crucible is provided for holding the material to be melted, and the heaters are installed around the crucible to provide heat to melt the material in the crucible. However, thermal energy tends to escape into the open space above the crucible through an opening thereon, and therefore it would take longer time to reach the melt point of the material, and the thermal energy provided by the heaters would be wasted unnecessarily.
To overcome this defect, there have been several types of crystal growth apparatuses designed to reduce the amount of thermal energy escaping through the opening of a crucible.
For example, a crystal growth apparatus disclosed in Taiwan utility model patent NO. M424337 has a thermal insulation cover provided on a crucible, wherein a surface of the thermal insulation cover is glossy or has a mirror surface thereon to reflect thermal radiation back into the crucible, which reduces heat dissipation.
In addition, another crystal growth apparatus disclosed in Taiwan invention patent NO. I405877 has a round quartz plate which is coated with gold provided on a crucible, wherein the surface coated with gold forms a reflective structure capable of reflecting thermal radiation back into the crucible to reduce heat dissipation.
The disclosures of the aforementioned patents both reduce heat dissipation by reflecting thermal radiation back into the crucible. However, in addition to radiation, thermal energy can be also transmitted through conduction and convection. Therefore, the designs of the conventional crystal growth apparatuses still have room for improvement to further prevent thermal energy from escaping out of the crucible.